a b s t r a c tIn this study, contributions of hemicellulose, cellulose and lignin to the mass and the porous properties of chars and activated carbons from various lignocellulosic materials were studied. A predictive calculation was established using the experimental results obtained for the three components separately to evaluate the carbonization and activation yields and their respective contributions to the chars and to the subsequent activated carbons of various precursors in term of weight fraction. These equations were validated. The results showed that lignin can be considering as being the major contributor of all chars and activated carbons. Besides, the evolution of the mean pore size versus the specific porous volume showed that each component contributes to the porosity of chars and activated carbons whatever is its weight contribution.

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Activated carbons are disorganized materials with variable pore size distributions (PSD). If one assumes that the porosity consists mainly of locally slit-shaped micropores, model isotherms can be obtained by computer simulations and used to assess the PSD on the basis of experimental isotherms. In the present study, CO isotherms have been measured at 273 K on

In this work, we report new experimental data of pure and binary adsorption equilibria of carbon dioxide and methane on the activated carbon RB2 at 273 and 298 K. The pressure range studied were 0-3.5 MPa for pure gases and 0-0.1 MPa for mixtures. The combination of the generalized Dubinin model to describe the pure CO 2 and CH 4 isotherms with the IAST (Ideal Adsorbed Solution Theory) for the mixtures provide a method for the calculation of the binary adsorption equilibria. This formulation predicts with acceptable accuracy the binary adsorption data and can easily be integrated in general dynamic simulation of PSA (pressure swing adsorption process) adsorption columns. It involves only three parameters, independent of the temperature, and directly determined with only one adsorption isotherm of CO 2 .

Microporous carbon blacks can be characterized by the same techniques as activated carbons, using the classical DR equation and comparison plots based on non-porous materials. The CO adsorption isotherm at 273 K, combined with 2 computer modelling, also leads to an assessment of microporosity. The results agree with independent techniques such as immersion calorimetry into liquids of variable molecular dimensions and a modified Dubinin equation. The study also confirms that the comparison plots based on N (77 K), CO (273 K) and C H (293 K) do not necessarily lead to overlapping results for the total micropore volume and the external surface area of the carbons.

The apparent and the real micropore size distributions (PSDs) of molecular sieve carbons can be assessed by combining the adsorption of CO 2 at 273 K with immersion calorimetry into liquids of increasing molecular dimensions. On the basis of model isotherms resulting from computer simulations, the adsorption of carbon dioxide, a relatively small probe, leads to the overall PSD of the carbon (essentially the internal micropore system). Immersion calorimetry, on the other hand, reveals the distribution of the pores accessible directly from the liquid phase, that is without constrictions. Liquid CS 2 probes the same volume as CO 2 and can be used as a reference. The paper describes the case of an industrial molecular sieve carbon obtained by blocking partly the entrance to a relatively broad micropore system, thus limiting its accessibility to molecules with diameters below 0.5-0.6 nm. It is shown how activation by steam at 900°C removes the constrictions and leads to a gradual overlap of the two PSDs. The distribution of the pore widths on the surface, observed directly by scanning tunnelling microscopy, is also given.

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